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Author Topic: C-14 carbon fuse electric profile  (Read 4707 times)

Offline bob branch

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C-14 carbon fuse electric profile
« on: July 21, 2011, 08:14:19 PM »
Over the last few years I have done some work with profiles with carbon fiber elements in the fuse to stiffen them up. I've done a number of them in RC models ranging from. 36 inch profiles to 1.20 size 3D profiles. I also did a build thread on the AMA district VII web site of a bashed profile version of Bob McDonald's full fuse Apogee stunter. Power was a PA .52. All of these consisted of carbon elements placed within a wood matrix, usually geodetic in form. Variations I have done include placing carbon fiber ribbons placed across the top and bottom of the fuse the length of the fuse, a fiberglass tube lengthwise in the fuse, a single carbon fiber tube lengthwise, and multiple carbon fiber tubes. Last year I did a 3D RC electric profile with only carbon fiber elements in the aft fuse. All of these have markedly improved the tail stability of the aircraft. As is well known in stunt, tail twist is a major problem in profile stunters. The next logical progression was to do a full carbon fiber tube fuse electric stunter, so that is the design motif for "C-12".

For expediency and for some comparison to the standard model I started with a Brodak P-40 ARC that I had on hand. The wing and tail elements will be applied as they come from the kit along with the main gear. The in wing control system will remain stock along with the control horns. I'll use a carbon fiber pushrod to the tail and a ball link there as is my usual practice. The moments have been changed completely to match those of the Brodak T-Rex so this will be a considerably longer plane than the P-40.

There are three primary fuse elements. The nose and motor mount section is made from a 1/2 inch thick sandwich of end grain balsa with a layer of carbon fiber on each side. All the carbon fiber tube elements of the fuse are 7/16 thin wall carbon fiber tube. Both of these are from Aerospace Composites. 7/16 tube was selected because the nose material could be routed to receive the tubes leaving the carbon fiber laminate on each side.  half inch balsa is used for the wing and horizontal stab cradles. They are routed so the tubing sits into them. They are slightly under contour of the tubes. Adhesive is 30 minutes epoxy with WEST Stystem microfiber adhesive filler #405. This is one of my preferred structural fillet additives. It is white in color and easily overlayed with finish fillet material or just painted. It is thixotropic which means it does not run. It stays where you put it. I mix it to peanut butter consistency, While in small amounts I usually use it with 5 minute epoxies, I am using 30 minute epoxy on this build since I have some larger batches to do for the wing cradles and motor section.

Here is a pic of the original basic layout.

bob branch
« Last Edit: July 25, 2011, 06:44:30 PM by bob branch »

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #1 on: July 21, 2011, 08:19:15 PM »
I have not decided on the motor as yet. A 3536 class motor will certainly do it well. An axi 2826/12 would be massive overkill. Basically I will get to the point where I can get a realistic cg measurement and chose the motor that balances it best from my inventory.

These are some pics of the nose material. The first shows how it comes. Then the routing for the tubes.
« Last Edit: July 21, 2011, 08:55:12 PM by bob branch »

Offline Crist Rigotti

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Re: C-14 carbon fuse electric profile
« Reply #2 on: July 21, 2011, 08:25:27 PM »
Pretty cool Bob!  Keep it coming!
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #3 on: July 21, 2011, 08:31:01 PM »
This is the nose section cut to shape. A Turnigy 3542 is shown just for motor cutout pattern. Anything I might use should fit the hole. Also filleting material I am using.

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #4 on: July 21, 2011, 08:35:11 PM »
opps! VD~ Murphy got in here!!

Well, onward I guess. Here are some pics after today's work.

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #5 on: July 21, 2011, 08:40:23 PM »
This shows the horizontal tail support. I should note that there will be no covering on the fuse except film. In fact its going to be transparent yellow. So all the structure will show. The white glue lines will be painted black as will the entire framework of the airplane prior to covering.

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #6 on: July 21, 2011, 08:52:52 PM »
Probably my biggest area of debate in this project was the motor area material and the diameter of the tubes. I was going to use smaller diameter thick wall tubing but it would have required a third tube and additional struts to get rigidity. The larger diameter thin wall tubing allowed me to use no other 3 dimensional structure but the tubes and their weight was less I think than the smaller diameter thick wall tubing would have been. Plus the routing of the balsa cradles allowed me to mount the wings more easily and tie them into the tubular structure with less question as to alignment. I could have pulled out a router table but its a tool buried in my shop since I stopped boat building so all the routing was just done with a dremel and a small sanding drum. This construction method was very fast. You are looking at about 3 or 4 hours work for what is now essentially a finished fuselage. Next I'll install the tail wheel, sand the fuse and cover it. Then I will install the wings and then cover them. The vertical stab, flaps, and elevator will get covered prior to installation. I'll post some more pics when I get further along.

bob branch

Offline Wynn Robins

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Re: C-14 carbon fuse electric profile
« Reply #7 on: July 21, 2011, 09:09:00 PM »
looks cool  - I did a similar thing a couple of years ago but used the square carbon tubes - they were a little heavy so gave up on it.......I like your light wall tube idea......might re-visit it myself......

will look awesome with transparent covering!!!
In the battle of airplane versus ground, the ground is yet to lose

Offline RickS

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Re: C-14 carbon fuse electric profile
« Reply #8 on: July 21, 2011, 11:40:45 PM »
Hi Bob,

Excellent job and process explanation.   I'm looking forward to the next "installment".

I'm sure  that the "twisted stab"   flying characteristic found in many profiles will be fixed with your body construction method.

 Once again...it looks great...and, I look forward to seeing it fly.

best,
Rick Sawicki

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Offline Dan Bregar

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Re: C-14 carbon fuse electric profile
« Reply #9 on: July 22, 2011, 04:10:33 AM »
Very cool Bob.  Interested in the ready to fly weight. I shall stay tuned. y1
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #10 on: July 22, 2011, 07:15:13 AM »
Dan

I too am interested in the weight. I have the profile kit fuse covered so I can compare weights. But This is not being built with weight as the primary consideration but rather rigity of the tailplane.  I did cut out several geodetic tubes from the original design concept. Contrary to general belief carbon fiber is not weightless nor is it lighter than balsa. Its structural stiffness is its advantage. There is still a lot of resin in it. The carbon itself is the least of the weight. Epoxy is heavy as we all learned in sheeted foam wings. But that is the advantage of thinner walled tubes. There are btw thinner walled tubes than these available. I have used them in wing tube receivers for RC spars. Not however as structural load carrying spars. Depending on how this works, that might be a next step, but its pretty weak stuff. Not sure it would be up to the task.

bob

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #11 on: July 22, 2011, 07:28:29 AM »
Crist and Rick: Thanks for the kind comments.

Wynn: I agree the square tubes would be a bit heavy. Round will give the least weight per size because of its lower surface area and less resin. It will also give more rigidity in multiple planes. It is more difficult to work with. In deciding on how to do the joints I went to the way full size tube frame aircraft weld the joints and just duplicated it in carbon fiber. I created the joints btw with the same small sanding drum in the dremel tool as I did the routing with. It turned out to be fairly quick and easy. I used coarse paper on the drum. The most difficult part was just keeping the two cuts in the same plane. To do this I marked the angle of the tube intersection on the geodetic member and cut it on the band saw. Then I used the dremel/sanding drum and put sanded the routed section of the tube. Hmmm. I'll have to get a picture of this and post it to get it clear I can see. At any rate the joints were each custom fit but they were pretty easy to do and wind up with less than a 1/32 in gap. The epoxy fillet needs some bulk to get its strength. But because the hollow ground cross section of the joint results in the fillet being internal in the tube the joint area is probably at least double the cross section of the tube. Its a really strong and stable joint. I can see why full scale tube fuse construction went primarily with round tube as well.  There is only 1 butt joint in the structure. It is the one under the horizontal stab cradle. I would have had to double the thickness of the balsa and it was not going to gain me any stiffness since the cradle joints are routed to the tubes on the other 3 sides. This one is just to carry the vertical compression load on the bottom of the not real deep balsa cradle.

bob

Offline john e. holliday

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Re: C-14 carbon fuse electric profile
« Reply #12 on: July 22, 2011, 09:00:27 AM »
This is very ingenious.  I like it. H^^
John E. "DOC" Holliday
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #13 on: July 22, 2011, 10:29:24 AM »
Thank you John.

bob

Offline david beazley

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Re: C-14 carbon fuse electric profile
« Reply #14 on: July 22, 2011, 01:13:31 PM »
This may be a non-issue, but any concern about the C/F being electrically conductive?
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #15 on: July 22, 2011, 01:28:11 PM »
David

No concern at all. I have flown all sorts of planes with a lot of carbon fiber in them. Besides no current is connected to the airframe. It is all in the power system. Interesting aside to that though is that in sailboats some sails have for years been made out of carbon fiber fabric. They do have an issue with electolysis and breakdown due to conductivity and contact with different materials... eg metal fittings. I just will make it a policy not to fly any of my planes on the deck of an aircraft carrier at sea.... UNLESS I'M INVITED!

bob

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #16 on: July 22, 2011, 01:31:20 PM »
Here are some pictures of the carbon tube joints I promised.

The first ones show a sample of tubing with the joint angle cut and the fishmouth having been created with the dremel and sanding drum.


Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #17 on: July 22, 2011, 01:33:19 PM »
Notice the bevel on the inside of the tube. The adhesive is placed on this bevel. The bevel increases the area of the bonded joint even further. This is a finished joint.

bob

Offline Jim Howell

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Re: C-14 carbon fuse electric profile
« Reply #18 on: July 22, 2011, 03:00:54 PM »
Bob,
Did you ever work up thin-wall steel tubing for homebuilt aircraft?  That pic of the junction of a longeron (?) with a diagonal member joined with epoxy looks just like what tried to achieve with an oxy-acetylene torch. (Never succeeded to my satisfaction for a junction that my life would depend on, so gave up on the idea of building that Skybolt.)
Jim Howell
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #19 on: July 22, 2011, 05:41:51 PM »
Jim

Yes that is where I got the inspiration for the joints. They are done the same way as you would do a welded joint. If I had ever learned to weld I would have built several full scale aircraft by now. I guess I could do a composite tube airframe. Some of the top aerobatic planes are done that way. What I did not realize until I saw the joint in my hand was how much extra stability the fishmouth gives the joint against rotation and the tremendous increase in glue area. Just what is needed for making things more rigid.

bob

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #20 on: July 23, 2011, 07:04:34 PM »
Next to the tail wheel mounting. I thought this was going to be a bit of a problem. I started with installing a traditional hardwood L routed to fit the bottom and elevator crutch support tubes. I was going to bend a wire to go thru the bottom tube and up into the slot on the L's bottom leg and glue that to the inside top surface of the bottom tube with the elevator crutch support tube for antirotation. But then I thought about it some more and wound up with a really simple solution.  #^ I used a grinding disk in the dremel to grind a slot for the stock Brodak tailgear wire. At the front of it I drilled a hole thru the top surface of the tube. I placed my epoxy fillet mix in the slot, dropped the wire into it so it set just under the tube's bottom surface and the vertical antirotation wire protruded thru the hole. The wire pushed the fillet blend above it. The wire sets within the tube wall, and a capping layer of fillet was placed over the wire in the slot and where it protrudes from the top of the tube to lock it in. Finally sanded smooth. Done. Simple, strong.

bob

Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #21 on: July 24, 2011, 02:09:41 PM »
EGADS hope that don't make the tail fall off!!!

All seriousness aside this is some SERIOUS structure.  I bet it is stiffer than the normal full fuselage.  Looking forward to seeing this one at the Detroit Signal Seekers meet August 20-21 (plug!)
Denny Adamisin
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #22 on: July 25, 2011, 06:32:37 PM »
Ok, now for quick advice to everyone. If you can build tonight, DO! Cancel whatever you are doing and get out in the shop and work fast. Cause I've got Murphy in mine and he's under lock and key and I don't know how much longer I can contain him! Last night I had finished fairing in the fuselage. I used fillet material to build the tube joints out so they would be flush with the film covering when its applied. Same with the wing and horizontal stab cradles. Got them all done. Leveled and sanded smooth. Doing really well. I had one can of black spray paint in the shop so I shot it real quick before I lost light in my spray booth... otherwise known as my boat house. Well, ok, light was involved, but at 8:08pm the Harsens Island Mosquitoes come out and.... well even those in Florida are impressed with these critters. So it was shoot and run. Left it out in the boathouse cause it was about 95 in there and I knew it would dry well. Got home this evening and.... well, from know on I will look very carefully at any spray can before I use it... it was black CRINKLE paint! Worked fabulously well on the instrument panel of the 1946 100% scale Ercoupe I restored to duplicate the original... but not so much the esthetic I was looking for with the carbon fiber.... especially not to cover over with film.  HB~> So I padlocked Murphy to the vice and set to sanding and reshot tonight. Got it all shot with appropriate paint this time and.... well, you get the idea.

However, C-14 has a theme as well and of course it revolves around the carbon fiber. The entire plane will be covered with transparent yellow ultracote. But just having balsa on the rest of the plane would just look out of place and loose the theme. So....

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #23 on: July 25, 2011, 06:41:07 PM »
Pic files were too big so I had to put them in two individual posts. The paint is just a generic black rattle can. Rustoleum indoor outdoor.... who needs fuel proof? And it will all be under film anyway so even at a contest is will not be an issue.. but I would never set my nice electric in a glow exhaust puddle anyway.  So next is covering it. I will not present that in detail since I covered the process in the build thread I did on the T-Rex that is here in the electric forum. If you are interested in learning how to do it its a good primer. But if you really want to learn to do it latch onto a good RC builder who has used it for years and learn from them. I'll post next when its covered.

bob

Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #24 on: July 25, 2011, 07:58:15 PM »
Crinkle paint?  In my experience that is the only kind there is  HB~>

C-14 is looking mighty fine, looking forward to the transluxcent stuff over the top...
Denny Adamisin
Fort Wayne, IN

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Offline john e. holliday

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Re: C-14 carbon fuse electric profile
« Reply #25 on: July 27, 2011, 08:54:28 AM »
That is looking great.   It will be awesome with the transparent covering.   H^^
John E. "DOC" Holliday
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #26 on: July 31, 2011, 05:46:33 PM »
Here is an update. I have the wing covered now and installed in the fuse and am finishing covering of the tail components and flaps. My idea for a color scheme did not work out. The translucent yellow on the black fuse components did not give a uniform color. It gave streaks where the film had bonded and had not. So I elected to cover the wood sheeted components with metallic purple ultracote. Covering and assembly should be finished this week. Hopefully I'll get first flights next weekend. I will be using one of Keith Renecle's timers on it to see how it compares performance wise with the Hubin units I usually. I would definately like to be able to use a less expensive esc than what we are locked into right now.  Updates as I get further along.

bob branch


Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #27 on: July 31, 2011, 06:04:09 PM »
Fair to partly awesome looking Bob!

BTW Bob brought the C-14 fuse out to the field yesterday.  I am sure this is the stiffest fuselage profile or full build that I have ever seen.   
Denny Adamisin
Fort Wayne, IN

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Re: C-14 carbon fuse electric profile
« Reply #28 on: August 02, 2011, 07:43:14 PM »
Agree with my little brother here. Light and EXTREEMLY stiff. Wonder if a I-beam wing built with a similar idea could be in the offing?

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #29 on: August 06, 2011, 12:47:22 PM »
Ok, the build is done. Time for pictures. Name and numbers are not on yet. I have to design and make those yet. Also electonics are not mounted. Power turned out to be a turnigy 3642 1000 KV. Timer will be KR and esc will be a Mystery 40 amp. This is a basic and simple RC timer I get from Hobby City. I think it will give me a nice opportunity to test the KR timer and compare it to the CC that I usually use. I've used these for years in RC with never a failure. More than I can say for you know who. The motor is a 5 oz class motor. I have several but this one was convenient. Battery will be 4S arrow wind 2800 mah and prop will be original apc 11X5.5EP.  Airframe weight with electronics is 46 ounces so 56 with the battery. Figure 5 oz of fuel on a glow model and this would be equivalent of a 51 ounce model in glow weight equivalent. It is the length of the T-Rex with same moments and uses the wings from the Brodak P-40 so 560 squares. As I have said this is an experiment primarily to decrease twist in profile fuselages. There was no effort to build light except for using thin wall tubing. From the way the rigidity has turned out my guess is flight tests will show we can go to a significantly smaller tube than the 7/16. But that is rushing it a bit. It has to be flown and trimmed first to see what we have. I will post final pics once I have name and numbers on and a flight test report once its sorted out. Oh, yea, those ARE 3 inch wheels. I'll be flying it in a contest in a couple of weeks on a field where they may be too small for the grass. ... happened last year.

bob branch


Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #30 on: August 06, 2011, 06:47:21 PM »
Now THAT looks like the real deal.  Congrats Bob.  Looking forward for the flight reports
Denny Adamisin
Fort Wayne, IN

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Offline frank carlisle

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Re: C-14 carbon fuse electric profile
« Reply #31 on: August 08, 2011, 12:33:07 PM »
Nice job Bob.
Frank Carlisle

Offline Jeff Traxler

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Re: C-14 carbon fuse electric profile
« Reply #32 on: August 08, 2011, 03:23:04 PM »
Hi Bob,
       Kinda looks like a semi-scale homebuilt.SWEET!!!!!!I will be up for the contest.Can't wait to see her fly.
If you wanna sing the blues(Fly Stunt) you gotta pay your dues and "I know it don't come easy"

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #33 on: August 08, 2011, 05:34:20 PM »
Dennis, Frank, & Jeff:

Thanks for your kind comments guys. Proof is in the flying and as of right now its still unproven. Tonight, however, I did some quantitative testing on the rigidity of the structure. For this test I used 3 models, the new C-14, an Ultraproducts Nobler, and a Brodak SV-11 arf. I wanted to be able to measure if this was a quantifiable improvement. I chose these models to compare to because they are well known standards to compare to. The wing area of the C-14 is closer to the nobler than the SV but the moments of the C-14 are more comparable to the SV.

For my test I placed each model on a Robart model stand. I removed the pivoting arms so that they would not influence the results. I placed the wing spar on the solid 1/2 inch wide foam support on one of the stand, and the aft fuselage rested on the back cross piece of the stand. This does place a slight advantage to the two full fuse ships as the width of the aft fuse which was about under the elevator hinge line could support the width of the fuse while on the C-14 it was a point contact at the bottom of the fuse radius. I measured out the horizontal stab from the center line of the fuse 12 inches. On the nobler I had to add a slight extension to get the line but not much. I wanted to place a one pound weight on each horizontal stab at this location and measure the deflection of the stab from level. The closest I could get to a pound in a shape I could get stable was a one pound one ounce lipo.  The following deflections were measured:

C-14 carbon fuselage model 3/8 inch
UHP nobler                        5/8 inch
Brodak SV-11                    3/8 inch

I think this shows some validity to the concept of using large diameter thin wall carbon tube in combination with balsa wing cradles to produce a profile structure that measures comparable aft fuse rigidity to a full fuse model. Most likely an improvement in the carbon fiber version could be attained by using the same carbon balsa composite laminate for the wing cradles as I did for the nose motor mount section.  However I do not think it would be substantial and the workability of getting an accurate fit would be decreased. Still, for a scratch build where I was assembling the wing and stab and had completely accurate patterns for both I would have done it. As for trial fitting two layers of carbon fiber and two layers of epoxy with a half inch end grain balsa sandwhich was not my idea of a fun time where the wings and stab were already built. This way I had no trouble getting accurate fits, alignments, and angles of attack with minimal work.

Most likely first flights will be this coming Friday. I will report on flight expereince after that though obviously trimming will go on for some while.

bob branch

Offline Crist Rigotti

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Re: C-14 carbon fuse electric profile
« Reply #34 on: August 08, 2011, 05:56:06 PM »
Very interesting stuff Bob.  Nice odel too!
Crist
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Offline Dan Bregar

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Re: C-14 carbon fuse electric profile
« Reply #35 on: August 08, 2011, 08:37:40 PM »
Bob

What is the ready to fly weight ?

Dan
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Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #36 on: August 10, 2011, 06:59:51 PM »
Dan

46 ounces with no battery. 56 oz with 2800 mah 4S Arrowind pack.

bob

Offline bob branch

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Re: C-14 carbon fuse electric profile
« Reply #37 on: August 13, 2011, 07:10:25 AM »
Well, time for the first flight report. What I had suspected turned out to be fact, the bird was tail heavy. This may be a suprise to some but as I said earlier, carbon fiber can be heavy. Certainly much heavier than balsa wood. Also remember though that no consolation was made to minimize weight. The purpose of this exercised was to attempt to create a profile structure that had the same tail performance as a full body structure. Weight issues could come later if the concept proved out. The wings were all stock out of the box unmodified Brodak P-40 components. So we know for instance right off the bat the tail is heavy. I was a bit surprised though because when I used the same moments as the T-Rex I felt the nose would be long enough to balance things out but if you look back at the profile view of the plane you will see there is very little carbon tube in front of the wing. The top and bottom tubes go into the motor mount laminate about 3 inches so the rest of the front end is pretty light.  I had chosen the Turnigy 3642 motor after doing a preliminary cg at home and finding I was going to need more weight in the front than the 3536 I originally planed had. I have a thread posted earlier regarding motor and battery selections to place cg where we want it and that was a large part of the first days' testing.

First, just to get it out of the way, it worked. 3 other experienced pilots observed the plane and as Rick Sawicki summarized, the tail stayed perfectly aligned. No twist whatsoever. Performance wise the plane flies very similar to to the T-Rex once we started to get near the right cg. When we started it obviously did not groove real well being tail heavy. Certainly not unflyable but not what we wanted. I started with 10 oz 4S Arrowind 4S pack and then started moving up thru pack sizes till we hit on the cg that locked the plane in and let it groove well in level flight. This wound up being a 5S turnigy lightmax 3000 mah pack. I was not going to 5S for power but just for the convenience of adding different amounts of weight and finding a cg position. We also tested a number of props in the 11 inch range both tractor and pusher configs. I that testing will continue for different reasons I'll get into in a minute.

Now how did it fly.... very smoothly... but with an absolutely wicked corner, just like the T-Rex. The corner was considerably better than the stock P-40 configuration. The exits were flat with no bobble. Line tension was good inside and outside.  Lap times on 63 ft lines I flew to were 5.3 seconds.  I did do a full pattern and it did everything very much within the range of where it can be trimmed to a very competitive plane without much trouble.

Now to the changes. I really do not want to drag the weight of a 5S pack around doing nothing but adding weight. Weight with function is fine. But obviously this size plane does not need 5S to fly on. So the motor is going to be changed to an Axi 2826/12. This will give me some more weight and the ability to generate more power and have a larger prop. I'll be able to turn considerably less rpm and have lower current draw. These are the advantages that led me under Rick Sawicki's guidance to the 2826/12 package. Normally I'd turn a 2826/12 with an apc 12X6ep in the low 8000 rpm range to generate a 5.2 sec lap on 63 ft lines. I may need to bend longer gear to do this off grass with the P-40's original short gear, but I do have a 12X6EP that I have cut down to 11 inch that may work well. We shall see. If I need to I'll just bend longer gear. Since I have to gain weight in the front end I'll also go to heavier components. I'll switch to an ICE 50 esc since that's the heaviest I have and then will fine tune the cg with battery and possibly spinner combinations.

Progression of the concept will be in decreasing the tubing diameter and thus decreasing the aft end weight and building a tail from light wood. The wing configurations worked out extremely well with the longer moments. The feel of this plane is much more that of a full bodied plane. The effect of eliminating the tail twist was very noticeable. Its also clear that no additional structure is required in the back of the plane. There are also premade tapering carbon fiber tubes available that would markedly decrease weight at the back end. I have used these in my boat building work and that would also be an area to evaluate. So that is about what I have to say for the Branch Profile Fuselage structure. Feel free to use it or modify it in any way you want. I am sure its very duplicable without any special talents. Please opst your mods and results and if you would perform the same test on stab deflection I used it would be helpful in assesing changes to the structure and their results. Also post the type of laminate you use on the carbon fiber or whatever material tubes you use. I know most of the tapered tubes are not straight fiber construction but woven fiber construction. Be interested in knowing the results if someone does that. Oh, and during the flying the transparent geodetic aft fuse was not a visual impairment to me at all. My eye keyed in on the yellow horizontal strip and the top and bottom rods. Because the fuselage is not constant height all the way back, the bottom tapers up the longitudinal stripe and top tube became my key features. Frank Carlisle who is a more traditional builder & flier said he was distracted by the geodetic appearance on the ground but made not comment regarding it in the air. He says he likes the traditional fuse cut out appearances better. But of course, it could be covered opaque or with silkspan or polyspan. Your choice. They will all work.

Next weekend I'll be flying its first contest with it and will post how that goes.

bob branch
« Last Edit: August 13, 2011, 07:49:05 AM by bob branch »

Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #38 on: August 13, 2011, 02:08:22 PM »
MOST excellent result, CONGRATS!  The heavier motor way out front might move the CG almost as much as the heavier batt pack aft did.  Heck if all else fails I think you still have that  AW 2832...

I am happy to hear your comparisons to the T-Rex too, I had hoped you could come close to the same feel for thus make the two airplanes as near the same as possible.

I used tapered booms in RC sailplanes - they would offer a tidy weight save while remaining very strong.  All in all a GREAT project, WELL DONE my friend!
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Brent Williams

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Re: C-14 carbon fuse electric profile
« Reply #39 on: June 27, 2018, 07:44:12 PM »
Ancient thread resurrection, yes!...

This seems pretty neat to me.

After exchanging a few emails with Bob B. and Dennis A., I have been quite tempted to attempt this.   Pricing of thin wall carbon tube isn't cheap, but the concept is very compelling.  Just curious if anyone else has tried this or a similar construction method?

Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline Dane Martin

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Re: C-14 carbon fuse electric profile
« Reply #40 on: June 27, 2018, 08:16:39 PM »
Ancient thread resurrection, yes!...

This seems pretty neat to me.

After exchanging a few emails with Bob B. and Dennis A., I have been quite tempted to attempt this.   Pricing of thin wall carbon tube isn't cheap, but the concept is very compelling.  Just curious if anyone else has tried this or a similar construction method?

Check here.
http://www.kitesandfunthings.com

Also, give him a call if you can't find what you need. He supplies plenty of rc kit makers with CF tube. I order tubing from him for my gliders. He is the manufacturer, so pricing is exceptional.

Offline Brent Williams

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Re: C-14 carbon fuse electric profile
« Reply #41 on: June 28, 2018, 11:16:08 PM »
Fair to partly awesome looking Bob!

BTW Bob brought the C-14 fuse out to the field yesterday.  I am sure this is the stiffest fuselage profile or full build that I have ever seen.

Dennis's corroboration regarding the stiffness of the carbon tube fuselage is what helps me feel like there is merit in this construction method.  It certainly looks neat if nothing else.
« Last Edit: July 04, 2018, 02:26:39 AM by Brent Williams »
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
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Offline Fred Underwood

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Re: C-14 carbon fuse electric profile
« Reply #42 on: June 29, 2018, 11:08:37 AM »
I found this thread and emailed Bob a couple of years back.  The structure reminded me of an exoskeleton car, Ariel Atom.  Here is some tubing that is fairly light.

https://www.rockwestcomposites.com/round-tubing/round-carbon-fiber-tubing/fabric-weave-carbon-tubing/45555
 
https://www.rockwestcomposites.com/round-tubing/round-carbon-fiber-tubing/fabric-weave-carbon-tubing/46322

An email to RockWest confirmed that the actual weight of 72" of the second listed is 2.3 oz.

Most carbon tubing is not light, or is expensive.  I'm still using 1/64" ply :)
Fred
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Offline Dennis Adamisin

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Re: C-14 carbon fuse electric profile
« Reply #43 on: August 07, 2018, 11:56:21 PM »
Dane posted a link to Kites & Things; these folks also offer tapered booms which would be a nice way to reduce the weight at tail.

A friend of mine built a "Naughty Girl" that had flexy fuse syndrome.  He embedded a 3/16 carbon tube in the top and bottom of the fuse that fixed it.  Helped that as finished it was nose heavy so the added beams just allowed him to remove tail ballast.

I have built exactly 1 fuse with 1/64 ply skins - was very disappointed in it; heavy and seemed no better than a balsa plank...
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!


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